   (chord :Eb4 :major)
   (chord :Eb4 :major)
   (chord :Bb3 :major)
-  (chord :Bb3 :major)
+  ()
 ])
 
 (def variation-section [

  (chord :Eb4 :major)
  (chord :Eb4 :major)
  (chord :Bb3 :major)
  (chord :Bb3 :major)
])


(defn play-chord [notes duration] ( do 
  (defn play-note [note] (organ-cornet note (/ duration (* 1000 0.9))))
  (let [
    root (first notes)
    bass (- root 12)
    with-bass (cons bass notes)
  ]
    (mix (map play-note (map midi->hz with-bass)))
  )
))

(def metro (metronome 250))
(defn beat-length [metro] (- (metro 1) (metro 0))) 

(defn play-progression [progression metro start] ( do
  (if (> (count progression) 0) (do
    (at (metro (+ start 0)) (play-chord (nth progression 0) (* 4 (beat-length metro))))
    (play-progression (rest progression) metro (+ start 4))
  ))

    (concat
      starting-section
      middle-section
      starting-section
      middle-section
      variation-section
    )
    metro
